Filtering a large quantity of biological samples (e.g, several thousand) is difficult to achieve in an effective manner, especially in the case of an analytic system that prepares injection volumes for high performance liquid chromatography. In order to ensure that a sample is not dispersed in the tubing of the system, it is necessary for the internal volumes to be as small as possible. This requires the use of a filter membrane with the smallest possible cross sectional area. In the case of a diluted blood sample, the filter is required to remove a significant volume of material in the form of lipids from the walls of the blood cells, rubber cap debris, etc.
Prior filter devices using a stainless steel mesh membrane were effective, but rendered unusable after only a few uses, in some cases as little as three. Backwashing the filter can extend life (e.g., up to 30 uses), but certainly not to the degree of having a useful system. Applying ultrasonic agitation to filters has been proposed to dislodge captured particles, which can then be backwashed. However, devices for doing so require a large amount of energy and can heat the sample to such a degree that denaturing can occur. Accordingly, there remains a need to provide a repeatedly effective filtering device.